The present invention relates to a thrust reverser for a turbofan-type turbojet engine, more particularly an air deflector for such a thrust reverser to minimize disturbances in the air when the thrust reverser is in the forward thrust position.
Turbofan-type turbojet engines are, of course, well known in the art and typically comprise an air duct located around the turbojet engine to direct air flow generated by a turbofan in a downstream direction to augment the thrust of the turbojet engine. Thrust reversers are also well known in the art and, when utilized on such turbofan engines with a high bypass ratio (e.g. the ratio of air passing through the air flow or cold flow duct with respect to the hot gas emanating from the turbojet engine exhaust) it is known to utilize the thrust reversers to redirect only the cold flow air passing though the air flow duct. Typically, such thrust reversers comprise one or more pivotable doors, movable between a forward thrust position in which the door is generally flush with the outer housing defining the outer oundary of the cold flow duct, and a thrust reversing position in which the forward edge of the door is moved outwardly such that a rear or downstream edge portion of the door blocks off the cold flow air duct so as to redirect the air in a direction having a reverse thrust component.
A typical thrust reverser is illustrated in FIGS. 1 and 2 wherein an outer housing 1 defining the outer boundary of the air flow duct is concentrically arranged about the turbojet engine (not shown). The outer housing comprises an outer surface panel 4, an inner surface panel 5 and a frame member 6 interconnecting the inner and outer panels.
A thrust reverser 2 has a movable thrust reverser door 7 comprising an outer surface panel 9, an inner surface panel 11 interconnected by a forward baffle 13 and a frame 12. A downstream rear collar 3 is fixed to the housing and defines the rearmost portion of the housing.
The thrust reverser door 7 is movable, in known fashion, between a closed, forward thrust position, shown in FIG. 1 and an open, thrust reversing position, shown in FIG. 2 by an actuator 7(a). The actuator 7(a) may comprise a cylinder attached to the frame 6 and having an extendible and retractable piston rod connected to the movable door 7. In its closed, or forward thrust position, the outer surface panel 9 of the thrust reverser door 7 is substantially flush with the outer surface panel 4 and the outer surface of rear collar 3 so as to provide a smooth air flow surface for the air passing in the direction of arrow 10. In its open or thrust reversing position, the rear portion of the door 7 blocks off the air flow duct and directs the air flowing through the duct, which normally flows in the direction of arrow 15, laterally outwardly through the opening in the housing in a direction having a rear thrust component. In order to maximize the efficiency of the door 7 when in the open position, baffle 13 extends beyond the surface of the inner panel 11 so as to redirect the air in a more forward direction thereby increasing the reverse thrust.
This configuration, when in the forward thrust position, creates a cavity 16 defined by inner panel 11, baffle 13, downstream air flow edge 8 and a line 14 defining the theoretical air flow between inner surface panel 5 and the rear collar 3 inner surface. The edge 8 is curved, as shown in FIG. 1, to allow air flow to pass through the housing during the reverse thrust operation. The cavity 16 creates disturbances in the air flow 15 through the cold flow duct when the thrust reverser door 7 is in its closed position resulting in a decrease in the overall efficiency of the turbofan.
Typical prior art thrust reversers can be found in French Pat. Nos. 2,486,153; 2,506,843; and 2,559,838. Attempts have been made to place the inner panel 11 in a position closer to the theoretical air flow line 14 when the thrust reverser door is in its closed position by either movably affixing the inner panel to the thrust reverser door, or forming baffle 13 such that it retracts when the door is in its closed position. Although the systems utilizing movable inner door panels and movable deflectors have somewhat alleviated the problem, these devices have increased complexity and manufacturing costs of the engine.